Need Help Modifying a Midland 13-857B CB to a 10 meter Beaco

[robo36]

Hello all, I am looking for information on modfying a OLD CYBERNET Midland CB Radio model 13-857B , to 28.000 to 28.299 MHz. Any information would be appreciated.
ROB

[raven666]

I do not believe the final in that radio will tolerate even CW at the duty cycle you will need.

[robo36]

Hello Raven666, well many Midlands are in use as Beacons , maybe not this model? Anyway a Final transistor could be changed if it gives up its SMOKE!
Thanks for your information.
rob

[Rick]

What is the PCB number?

[raven666]

Hello Raven666, well many Midlands are in use as Beacons , maybe not this model?
rob

You learn something new everyday. I had no idea

[robo36]

Hello Rick the number of the PC Board is PTBM039AOX.
hOPEFULLY YOU HAVE SOMETHING ON THIS bOARD?
THANKS FOR ANY HELP.
rOB

[Rick]

I assume your Midland is a 40-channel model, as the early version was only 23-channel.

Change the 11.8066MHz rock.
12.1533MHz will give you from 28.005MHz to 28.445MHz.
12.3033MHz will give you from 28.455MHz to 28.895MHz.
12.4533MHz will give you from 28.905MHz to 29.345MHz.

You could makeup a switch circuit to switch in the rocks using a 3-position switch 3 chokes, 3 1N4148 diodes and 3 20pF trimmers.

It goes with out saying that you will need realign the RX and TX strip.

[robo36]

!
Hello again RIck , The Midland is a 23 Channel Radio and I am still looking for a Schematic and Board layout!
Are the Crytasl you mentioed the same for the 23 Channel?
thanks ROb

[Rick]

Yes, the crystals are the same.
It has been along time since I last work on the PTBM039AOX chassis, but seam to remember that they is a link wire around the channel switch which you remove to make it in to a 40-channel model.

You can also get all the channels you want using an EPROM, Check out this link http://www.radiomods.co.nz/addon_pll02amanual.html
If the Defpom no longer builds the EPROM board, Ask Dave (Zodiac) he comes on this forum from time to time, he is the kid for EPROM’s.